The present attractive features of the latest type of reciprocating, double-acting Stirling engine (Philips), leads to the advocacy of the double acting principle for a rotary version of this closed cycle engine design.
The reciprocating configuration does not follow the classic Stirling cycle since there is no distinct displacement function as a separate element in the present engine. The engine is double-acting in that adjacent pistons serve the displacement action for each piston in the group for alternate cooperation.
The main advantages in the reciprocating, double-acting arrangement are a highly concentrated piston/-volume density with greatly improved heat transfer through the use of a large number of small transfer tubes, with effective regeneration provision.
An additional advantage is that all pistons now produce a useful power output without the relative load losses of the previous separate displacer pistons.
The power transmission package is simplified by using a swash plate drive without a pressurized crankcase, as in the past design. A smooth power flow results from four pistons, phased ninety degrees apart with a natural balance between all the operating parts.
The use of the swash plate drive does entail large thrust vector and frictional losses which are apparently acceptable because of the several basic advantages in the configuration.
Previous rotary Stirling cycle engines have been unsuccessful due to poor heat transfer provisions and low compression ratios, in addition to power losses sustained from a separate displacer rotor. With the adoption of the series or double-acting principle and the application of a large number of small transfer tubes, as in the recip engine, it is probable that a rotary, near-counterpart of the double-acting Stirling engine will lead to a successful commercial engine system.
Although a rotary version cannot duplicate the compression ratio and distinct piston motion lag of a reciprocating engine, it will have some inherent advantages of its own, which are simplified geometric structure with reduced friction and thrust vector losses.
The inertia effect and simplified balancing with minimized drag are basic advantages, along with lower fabrication and assembly costs.
Because this rotary closed cycle engine utilizes a non-contacting vane, minimum friction rotary unit(s) it bears some relationship to the Brayton closed cycle turbine, in addition to the latest Stirling reciprocating engine design.
The current pressing need for seeking fuels other than petroleum based fuels makes the adoption of hydrogen attractive in view of its several advantages.
Decentralized, independent electrical power generating systems are highly desirable in many large cities where utility power sources have become overloaded and are currently unreliable. In addition, decentralized self-contained electrical power systems will be easier to troubleshoot, without the necessity of digging up underground feeder cables.